Explosive system

ABSTRACT

A steel tube having a flattened or oval cross section contains a pair of explosive cores. A sheath of pliable material such as silicone rubber surrounds and holds the core separated from each other and generally centered with respect to the steel tube. The rubber (1) protects the explosive cores from environmental temperature changes, and (2) absorbs the shock of detonation such that one of the cores may be detonated while the other remains undetonated as a reserve for redundancy of the system. Upon detonation of an explosive core, the steel tube expands from the flattened or oval cross section to a circular cross section; whereupon a pair of doublers enclosing the tube are fractured and separated along a weakened section underlying a notch or groove which extends longitudinally along a doubler joint and along the steel tube.

Elite States Patent Brandt et all.

[451 Oct. 17,1972

1 1 EXKLQSTVE SYSTEM [72] Inventors: Oscar E. Brandt, Saratoga, Calif.;

Joseph G. Harris, Dallas, Tex.

[73] Assignee: Lockheed Aircraft Corporation,

Burbank, Calif.

[22 Filed: Feb. 27, 1970 21 Appl.No.:15,032

[52] US. Cl. ..89/l B, 102/495 [51] Int. Cl... ..F42b 1/00 [58] Field ofSearch ..102/49.5, 22-24; 89/1 B, 1.5 F

[56] References Cited UNITED STATES PATENTS 3,311,056 3/1967 Noddin..102/27 3,486,410 12/1969 Drexelius et al ..89/l B X PrimaryExaminer-Samuel W. Engle Attorney-Richard l-l. Bryer and George C.Sullivan [57] ABSTRACT A steel tube having a flattened or oval crosssection contains a pair of explosive cores. A sheath of pliable materialsuch as silicone rubber surrounds and holds the core separated from eachother and generally centered with respect to the steel tube. The rubber(l) protects the explosive cores from environmental temperature changes,and (2) absorbs the shock of detonation such that one of the cores maybe detonated while the other remains undetonated as a reserve forredundancy of the system. Upon detonation of an explosive core, thesteel tube expands from the flattened or oval cross section to acircular cross section; whereupon a pair of doublers enclosing the tubeare fractured and separated along a weakened section underlying a notchor groove which extends longitudinally along a doubler joint and alongthe steel tube.

7 Claims, 5 Drawing Figures PATENTEDnm 17 I972 SHEET 2 BF 2 FIG. 3A

FIG. 4

OSCAR E. BRANDT JOSEPH G. HARRIS INVENTORS.

EXPLOSIVE SYSTEM BACKGROUND OF THE INVENTION This invention relates toan explosive system capable of totally confining the products ofexplosion; and more particularly this invention provides an explosiveseparation system which will remain operative in a wide range ofenvironmental temperatures and which will separate the parts with aminimum of shock.

Heretofore, elongated cords or ropes of explosives have been utilized inmany types of ordnance devices as well as in missile and satelliteseparation systems. U.S. Pat. No. 3,373,686 granted to .I. W. Blain andA. B. Leaman on Mar. 19, 1968, describes an explosive separation systemwherein a core of explosive material is detonated within a radiallyexpandable sheath. The sheath initially encloses the explosive core witha small cross section, and after detonation, the sheath in an expandedcross section continues to contain the gaseous products of the explosionto prevent contamination of the surrounding region.

The configuration described by U.S. Pat. No. 3,373,686 is successful ina limited range of temperatures. Should the ambient temperatures varygreatly above or below a normal room temperature, the configuration willburst or shatter and release contaminants into the surrounding space. Incontrast, the instant invention provides a configuration which willremain intact and confine all products of detonation and othercontaminants over a temperature range from 300 F to approximately 400 or500 F.

In explosive systems, it is desirable to have a high degree ofreliability. One method for achieving good reliability is through theuse of redundancy in the systems. In the event that one part or systemfails to function properly, a redundant part or redundant system mayprovide a back up protection to assure that the particular function isperformed and that the overall operation of the ordnance device ormissile or space vehicle is not impaired. One method for providing aredundancy is to simultaneously detonate both ends of an explosive cordor explosive core. If the explosive core is defective at one point, thisredundancy will provide a proper operation of the system since the twodetonations moving from both ends will traverse the entire length of thecore and will meet at the defective point. This type of redundancy wouldfail if there were two or more defective points in the explosive coresuch that two detonations traveling from the ends would be blocked atdifferent points leaving a segment undetonated and with the parts notcompletely separated. A further redundancy may be desirable to permit asecond detonation in the event that the first detonation is notcomplete.

It is an object of this invention to provide an improved explosivesystem wherein more than one explosive core is used within a singlesteel tube or expandable sheath and wherein the explosive cores are heldapart from each other by a shock absorbing material such that thedetonation of one core will not cause detonation of the other core.

It is a further object to provide an improved explosive system forseparation of parts with a minimum of shock imparted to the parts, andmore particularly it is an object to surround the explosive core(s) witha shock absorbing material within an expandable tube,

such that' the tube is expanded principally by the gaseous pressure ofthe products of the explosion and also by shock waves from theexplosion.

The ambient or environmental temperatures may vary considerably forordnance devices or missile or space vehicles, and it is another objectof this invention to provide an improved explosive system which will beoperative over a wide range of environmental temperature. Moreparticularly, it is an object to encase the explosive core(s) in athermal insulating and shock absorbing material such that the explosivecore(s) will be protected from both external shock and from temperatureextremes to remain functional over an extended time period.

I SUMMARY OF THE INVENTION According to a preferred embodiment of theinvention, the explosive system comprises an expandable tubular member,for example, an oval or flattened stainless steel tube, positionedagainst a separation member. The expandable member contains a shockabsorbing material such as silicone rubber having two separated cavitiesto receive cores of an explosive material. In the completed assembly,the cores are encased and held separated from each other by the shockabsorbing material which fills the expandable tubular member. Upondetonation of the explosive core, gaseous detonation products expand thetubular member against and rupture the separation member, with thedetonation products being contained by the tubular member which uponexpansion remains continuous, that is, does not rupture.

DESCRIPTION OF THE DRAWING The various features and advantages of thisinvention will become apparent upon consideration of the followingdescription taken in connection with the accom' panying drawing of thepreferred embodiment of this invention. The views of the drawing are asfollows:

FIG. 1 is a plane view of the explosive separation system of thisinvention;

FIG. 2 is a section along the line 2-2 of FIG. 1 showing in crosssection the steel tube with the explosive cores and rubber sheaththerein;

FIG. 3A and 3B are similar sections along the line 3-3 of FIG. 1 whereinFIG. 3A is a cross section of the assembly before detonation andseparation, and FIG. 3B is a cross section after the detonation of oneof the explosive cores and during the separation of parts; and

FIG. 4 is a section along the line 4-4 of FIG. 1 showing a detonatorassembly in cross section.

DESCRIPTION OF THE PREFERRED EMBODIM ENT As shown in FIGS. 1 and 3A, twoparts or bulkheads l l and 12 are connected together by doubler members13 and 14. The edges of the bulkheads 11 and 12 are sandwiched betweenthe doublers which are fastened together with means such as bolts 15.The doublers are elongated strips or plates of aluminum or othermaterial and may be generally flat or planar as illustrated, or may beof a special shape and configuration required by a missile, spacevehicle or any other structure which is to be explosively separated. Thedoublers may comthe offset centers provide a space therebetween forcontaining a stainless steel tube 19.

As shown in FIGS. 2 and 3A, the steel tube 19 is initially in an oval orflattened configuration, and is dimensioned to nearly fill the spacebetween the offset central parts 18 of the doublers l3 and 14. A grooveor notch 21 is formed in the doubler members 13 and 14, and extendslongitudinally intermediately between the flanges. The section ofmaterial underlying the groove 21 is thinner, and therefore weaker, thanthe other parts of the doubler. Thus, it may be appreciated that thedoubler is formed with a weakened central section which is more easilybreakable than other parts of the assembly. When the steel tube 19 isexpected to a circular configuration as shown in FIG. 3B, the centralparts of the doubler members 13 and 14 are forced outwardly, and eachdoubler will rupture or break along the weakened section underlying thegroove 21. With the doublers ruptured as shown, the parts 11 and 12 areseparated and are free to move apart from each other.

The stainless steel tube 19, as shown in FIG. 2, is formed generally inan oval shape with two spaced apart flat sides and two semicircular orotherwise rounded edges. A sheath of silicone rubber 22 or othersuitable shock absorbing and thermal insulating material is shaped tosubstantially fill the cavity within the stainless steel tube 19. Therubber sheath 22 contains two cylindrical holes or cavities containingexplosive cores 23 and 24. The silicone rubber sheath 22 holds the twocores 23 and 24 approximately centered with respect to the stainlesssteel tube 19 and spaced apart from each other.

The silicone rubber sheath performs several functions. Firstly, thesheath supports and holds the explosive cores in proper positions,separated from each other and generally centered in the assembly.Secondly, the silicone rubber, as a thermal insulator, protects theexplosive cores from sudden temperature variations through which thecomponents of a missile or space craft may pass. Thirdly, the shockabsorbing qualities of the rubber will protect the cores from externalshock to which a missile may be subjected during launching and duringsubsequent operations of rocket engines, etc. And fourthly, the shock ofdetonation of an explosive core is minimized, such that the secondexplosive core will not be detonated from the shock waves of thedetonation of the first explosive core, and such that a minimum shockwill be imparted to surrounding parts such as the bulkheads 1 1 and 12.

As shown in FIG. 1, two detonator blocks 25 and 26 are welded orotherwise attached to the stainless steel tube 19. The ends of therubber sheath 22 are split apart or bifurcated, such that the two cores23 and 24 are each extended to a position in spaced relation to aseparate detonating fuse 27, 28, 29 and 30. As shown in FIG. 4, the endsof the explosive cores 23 and 24 are extended into close proximity withthe ends of the detonator devices 27 and 28. The detonator devices 27and 28 are of a commercially available type which may be screwed into athreaded opening and will constitute a plug therein. These devices maybe detonated electrically from control circuitry not shown.

Since each end of each explosive core 23 and 24 may be separatelydetonated, a redundancy is provided to improve the reliability of theoverall system. In operation, one of the explosive cores 23 may bedetonated simultaneously at both ends thereof by the detonators 27 and29. Obviously, if one of the detonators 27 or 29 failed to operate, thecore would be detonated by the other, and the detonation would travelthe length of the core to effect the desired separation of parts. Thus,the simultaneous detonation of both ends of an explosive core insures aproper operation of the system even though one of the detonators maymalfunction. In the event that there is a break in the explosive core23, the simultaneous detonation of both ends thereof will insure aproper operation of the system, since the two detonations would,together, traverse the entire length of the core from each end towardthe break point.

The second explosive core 24 provides a further reliability in thesystem in the form of a back-up protection. Thus, if the detonation ofthe first core 23 failed or was not complete, the second core 24 couldbe detonated. In practice, the control circuitry extends through anelectrical disconnect junction which would be disconnected and separatedwhen the parts 11 and 12 were separated. The control circuitry willprovide a second electrical impulse to cause detonation of the back-upcore 24 in 600 to 1,000 milliseconds subsequent to the detonation of theprimary core 23. If during this time interval, the first detonation issuccessful and a separation of parts is effected; then the electricaldisconnect will be pulled apart; and the second electrical impulse willnot reach the detonator devices 28 and 30, to initiate the seconddetonation. On the other hand, should the detonation of the firstexplosive core 23 by faulty; the separation of parts 11 and 12 will notbe effected, and the electrical disconnect junction will remain intactsuch that the second electrical impulse will indeed be transmitted tothe detonator devices 28 and 30 for the detonation of the back-up core24.

As shown in FIG. 3B, the detonation of the first explosive core willcause the stainless steel tube 19 to expand to a circularconfigurationor cross section. The expansion of the steel tube 19, deforms thecentral parts of the doubler members 13 and 14, and ruptures theweakened sections underlying the longitudinal groove or notch 21. Sincethe silicone rubber sheath 22 absorbs much of the shock from theexplosive, the principle force causing expansion of the steel tube 19 isthe high pressure front generated within the tube by the gaseousproducts of the explosion. As shown in FIG. 3B, the silicone rubbersheath may be ruptured at various points leaving cracks and fissures inthe vicinity of the explosion or the position of the core 23 which wasconsumed by the detonation. The expansion of the rubber sheath'22 and ofthe steel tube 19 does not detonate the back-up core 24, which remainsencased in silicone rubber as shown in FIG. 3B.

When the doubler members 13 and 14 break as shown by FIG. 3B, the parts11 and 12 are no longer held together, and presumably there will be animmediate separation with the bulkhead or part 11 moving to the left (inFIG. 3B), and the bulkhead or part 12 moving to the right. The stainlesssteel tube, containing the unused explosive core 24 and containing theproducts of the explosion must not be allowed to fall out of theruptured cavity between the doublers to become a loose part, free fromboth the parts 11 and 12. Therefore, bands or straps 32 encircle thesteel tube H9 at periodic intervals as shown in FIG. 1 and are fastenedto one side only of the doubler assembly. As shown in FIG. 1, 3A and 3Ba convenient method for attachment is to extend the ends of each strapunder the flange side of the doubler member with a bolt extendingtherethrough. These bands 32 may be formed of a ductile material such assoft steel which is flexible and capable of expansion as the steel tube19 expands, such that the bands or straps 32 will not break as thedoubler breaks and the parts separate. Ordinarily the bands 32 should beattached to that side of the doubler connected to the part which is tobe discarded after separation. Thus, for example, the part 11 may be aportion of a satelite or space vehicle, and the part 12 may be of anearly stage rocket engine. After the rocket engine has completed itsburn and imparted its thrust to the space vehicle, it will be separatedand discarded. Similarly, after the steel tube 19 has expanded and hasperformed its function, it will likewise be discarded. By strapping thesteel tube 19 to the side connected with the part 12 which is to bediscarded, the tube with the unused explosive core 24, will likewise bediscarded from the still useful part 111 of the space vehicle. Thedetonator blocks at each end of the tube may be bolted or otherwiseattached to the same part as that to which the straps are attached toprovide a rigid support for the discarded assembly.

The explosive separation system of this invention provides a reliablemeans for separating parts with a minimum shock imparted to surroundingstructures. The stainless steel tube contains the gaseous products ofthe explosion after the detonation and separation of the parts whichthereby protects other parts and components of the assembly fromcontamination of the explosive gases. Because of the thermal insulatingand shock absorbing qualities of the rubber sheath, the explosive coresare protected from damage due to environment temperature change and dueto external shock. These features enhance the reliability of the system,and the reliability is further enhanced by the redundancy provided by asecond or back-up explosive core, which need not be detonated at thesame time of the detonation of the first or primary core; but may beheld in reserve for later time if needed.

What is claimed is:

l. A low shock explosive system comprising:

a separation member including an elongated plate with a rupturableweakened section;

an expandable metal tubular member;

means for closely confining said tubular member adjacent to the weakenedsection of the separation member in the path of expansion of saidtubular member,

said tubular member being elongaged in one dimension in cross-section;

a pair of explosive cores continuously spaced apart in said elongagedimension and positioned within the cavity formed by said tubular memberand extending continuously through said tubular member;

a thermal insulating and shock absorbing material surrounding both saidexplosive cores and encased within and substantially filling the cavityformed b the tubular member sal material continuously separating saidexplosive cores and preventing cross-detonation therebetween;

and means for separately detonating the explosive cores so that gaseousdetonation products expand the tubular member while being containedthereby and so that the tubular member will expand against and rupturethe separation member.

2. A low shock explosive system in accordance with claim 1 wherein theseparation member comprises two generally 'planar and parallel doublersfastened together with the tubular member there between, each doublerbeing an elongated strip and having flange parts along each edge andcentral part connecting the flanges, said flanges being fastenedtogether and adapted to hold a structural part to be separatedtherebetween, said central parts being offset from each other to providesufficient space to contain the tubular member in an initial ovalconfiguration, said central part of each doubler having a weakenedsection extending longitudinally to provide a line for rupture andseparation when the explosive'core is detonated and the tubular memberexpands from the oval configuration to a circular configuration.

3. A low shock explosive system in accordance with claim 2 wherein theweakened section of the doubler comprises a relatively thin section ofmaterial which underlies a notch formed in each doubler, said notchbeing centered in the offset central part midway between the edgeflanges.

4. A low shock explosive system in accordance with claim 2 furthercomprising a plurality of straps encircling the tubular member betweenthe doublers and fastened to the flanges on one side of the doublers,said straps being operable to hold the tubular member to one side of thedoubler after detonation of the explosive core and after the doublershave ruptured and separated in two parts.

5. A low shock explosive system in accordance with claim 1 furthercomprising a detonator assembly attached to the end of the tubularmember for initiating detonation of the explosive cores, said detonatorassembly containing two electrically actuable detonators, each of theexplosive cores having an end extending to a respective detonator.

6. A low shock explosive system in accordance with claim 5 wherein thedetonator assembly includes a metal plate to which an end of the tubularmember is attached, and wherein the explosive cores entrend through ahole in the metal plate to the detonator.

7. A low shock explosive system in accordance with claim 5 wherein twodetonation assemblies are provided, one detonation assembly beingattached to each end of the tubular member whereby the explosive coresmay be detonated simultaneously from both ends.

1. A low shock explosive system comprising: a separation memberincluding an elongated plate with a rupturable weakened section; anexpandable metal tubular member; means for closely confining saidtubular member adjacent to the weakened section of the separation memberin the path of expansion of said tubular member, said tubular memberbeing elongaged in one dimension in crosssection; a pair of explosivecores continuously spaced apart in said elongage dimension andpositioned within the cavity formed by said tubular member and extendingcontinuously through said tubular member; a thermal insulating and shockabsorbing material surrounding both said explosive cores and encasedwithin and substantially filling the cavity formed by the tubularmember, said material continuously separating said explosive cores andpreventing cross-detonation therebetween; and means for separatelydetonating the explosive cores so that gaseous detonation productsexpand the tubular member while being contained thereby and so that thetubular member will expand against and rupture the separation member. 2.A low shock explosive system in accordance with claim 1 wherein theseparation member comprises two generally planar and parallel doublersfastened together with the tubular member there between, each doublerbeing an elongated strip and having flange parts along each edge andcentral part connecting the flanges, said flanges being fastenedtogether and adapted to hold a structural part to be separatedtherebetween, said central parts being offset from each other to providesufficient space to contain the tubular member in an initial ovalconfiguration, said central part of each doubler having a weakenedsection extending longitudinally to provide a line for rupture andseparation when the explosive core is detonated and the tubular memberexpands from the oval configuration to a circular configuration.
 3. Alow shock explosive system in accordance with claim 2 wherein theweakened section of the doubler comprises a relatively thin section ofmaterial which underlies a notch formed in each doubler, said notchbeing centered in the offset central part midway between the edgeflanges.
 4. A low shock explosive system in accordance with claim 2further comprising a plurality of straps encircling the tubular memberbetween the doublers and fastened to the flanges on one side of thedoublers, said straps being operable to hold the tubular member to oneside of the doubler after detonation of the explosive core and after thedoublers have ruptured and separated in two parts.
 5. A low shoCkexplosive system in accordance with claim 1 further comprising adetonator assembly attached to the end of the tubular member forinitiating detonation of the explosive cores, said detonator assemblycontaining two electrically actuable detonators, each of the explosivecores having an end extending to a respective detonator.
 6. A low shockexplosive system in accordance with claim 5 wherein the detonatorassembly includes a metal plate to which an end of the tubular member isattached, and wherein the explosive cores entrend through a hole in themetal plate to the detonator.
 7. A low shock explosive system inaccordance with claim 5 wherein two detonation assemblies are provided,one detonation assembly being attached to each end of the tubular memberwhereby the explosive cores may be detonated simultaneously from bothends.